Why Greta Van Susteren is leaving Fox News so suddenly

A sharp knock on the door signaled that Greta Van Susteren's time on Fox News Channel was over.

A courier arrived at Van Susteren's Washington, D.C. home at 9 a.m. Tuesday, hand-delivering two letters that said that Van Susteren "was being taken off the air" immediately, according to her husband, John Coale, who is a high-profile Washington lawyer.

Van Susteren was already planning to leave, but she thought she would be hosting her 7 p.m. program "On the Record" for a few more weeks.

Yanking her off the air without a chance to say goodbye was "a bit immature," Coale remarked.

It was also a message from Rupert Murdoch.

Van Susteren has been one of the top anchors at Fox News for the past 14 years.

Murdoch, the patriarch of Fox's parent company 21st Century Fox, disliked her recent attempt to renegotiate her contract, and the unusual courier visit was a result of that, said one of the sources interviewed for this story.

The messy breakup is the latest sign of tension -- "chaos," according to Coale -- behind the scenes at Fox News.

Coale said Tuesday afternoon that there's "possible litigation in the future" between Van Susteren and Fox. He declined to elaborate.

Fox News declined to comment on Coale's remarks.

The network announced her departure less than an hour after the courier arrived. Van Susteren was not quoted in the press release.

Fox then deleted the "On the Record" web site, Van Susteren's biography, and her pioneering Gretawire blog -- essentially erasing her from FoxNews.com.

Fox "has not felt like home to me for a few years and I took advantage of the clause in my contract which allows me to leave now," she wrote.

That clause is known as a "key man clause." It was triggered by Fox News chief Roger Ailes' resignation in late July amid a sexual harassment scandal. Once Ailes left, Van Susteren had a chance to leave too.

The sources said Van Susteren sought to renegotiate the terms of her contract -- and asked for a big bump in pay -- after Ailes resigned.

Fox executives refused to negotiate, one of the sources said.

There was a "financial disagreement," another one of the sources said.

Van Susteren was motivated to leave in part because she had been unhappy and uncomfortable with the way Ailes ran the network the past few years, and with the way the network was perceived, two of the sources said.

Even while vocally defending Fox in public, she had concerns in private.

"It didn't appear it was getting better" after Ailes left, one of the sources said, so she looked to the exit.

Van Susteren had a 60-day period of time to invoke the escape clause after Ailes resigned. With time running out, Van Susteren sent a letter to Fox last Thursday night, informing the network of her decision.

The goal, Coale said, was to arrange a graceful exit. He said Van Susteren expected to continue hosting for weeks "to help them sort things out and have a smooth transition."

Indeed, television hosts normally have some time on the air after it is known that they're leaving. But not this time.

Brit Hume, the former 6 p.m. host who now serves as a Fox political analyst, is taking over Van Susteren's 7 p.m. time slot until election day.

Van Susteren said on Facebook that she hopes "to continue my career in broadcasting." A former criminal defense and civil trial lawyer, she joined Fox News from CNN in 2002 and has hosted "On The Record" ever since.

She cannot leap to a new network right away, however, due to the terms of her Fox contract. It is unclear how long the waiting period is supposed to last.

Fox News announced Van Susteren's departure just a few minutes after the channel's parent company, 21st Century Fox, confirmed a $20 million settlement deal with Gretchen Carlson, the anchorwoman who sued Ailes in July, starting the chain of events that led to his ouster.